Contact device and electromagnetic relay

ABSTRACT

A contact device includes a pair of fixed contacts, a movable contactor, a contactor holder, a movable shaft, and a base. The pair of fixed contacts are aligned in a first direction. The movable contactor comes into or out of contact with the pair of fixed contacts in a second direction orthogonal to the first direction. The contactor holder holds the movable contactor. The movable shaft moves the contactor holder in the second direction so that the movable contactor comes into or out of contact with the fixed contacts. The base accommodates the fixed contacts, the movable contactor, and the contactor holder. The base has a projection projecting from a position opposing the contactor holder in a third direction orthogonal to both the first and second directions.

BACKGROUND

1. Technical Field

The present disclosure relates to a contact device and anelectromagnetic relay including it.

2. Background Art

Well-known conventional contact devices include fixed contacts and amovable contactor, which comes into or out of contact with the fixedcontacts. A contact device disclosed in Japanese Unexamined PatentApplication Publication No. 2012-22982 includes a holder holding amovable contactor, and a movable shaft connected to the holder.

SUMMARY

The present disclosure provides a contact device having a simplestructure and a sufficient arc space to prevent an arc-over, and also anelectromagnetic relay including such a contact device.

The contact device of present disclosure includes a pair of fixedcontacts, a movable contactor, a contactor holder, a movable shaft, anda base. The pair of fixed contacts are aligned in a first direction. Themovable contactor comes into or out of contact with the pair of fixedcontacts in a second direction orthogonal to the first direction. Thecontactor holder holds the movable contactor. The movable shaft movesthe contactor holder in the second direction so that the movablecontactor comes into or out of contact with the fixed contacts. The baseaccommodates the fixed contacts, the movable contactor, and thecontactor holder. The base has a projection projecting from a positionopposing the contactor holder in a third direction orthogonal to boththe first and second directions.

The electromagnetic relay of the present disclosure includes theabove-mentioned contact device, and a driving device which drives themovable shaft so that the movable contactor comes into or out of contactwith the fixed contacts. The contact device and the electromagneticrelay of the present disclosure have a sufficient arc space to preventan arc-over.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an external perspective view of an electromagnetic relayaccording to a first exemplary embodiment of the present disclosure.

FIG. 2 is a sectional view of the electromagnetic relay taken along lineII-II of FIG. 1.

FIG. 3 is a sectional view of the electromagnetic relay taken along lineof FIG. 1.

FIG. 4 is a sectional view of the electromagnetic relay taken along lineIV-IV of FIG. 1.

FIG. 5 is a sectional view showing a state where a movable contactorshown in FIG. 2 twists.

FIG. 6 is an enlarged sectional view showing a state where the movablecontactor shown in FIG. 4 twists.

FIG. 7 is a partially enlarged view of FIG. 6.

FIG. 8 is a sectional view of a modified example of the electromagneticrelay according to the first exemplary embodiment of the presentdisclosure.

FIG. 9 is a sectional view of another modified example of theelectromagnetic relay according to the first exemplary embodiment of thepresent disclosure.

FIG. 10 is an enlarged view of an essential part of an electromagneticrelay according to a second exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Problems associated with the conventional contact device will now bedescribed briefly prior to describing exemplary embodiments of thepresent disclosure.

In the above-mentioned conventional contact device disclosed in JapaneseUnexamined Patent Application Publication No. 2012-22982, the contactorholder (holder) comes into contact with the inner surface of the base toregulate the rotation (twist) of the contactor holder and the movablecontactor.

In this contact device, however, while the contactor holder and themovable contactor twists, the movable contactor and the inner surface ofthe base come too close to each other to have a sufficient arc spacerequired for current interruption.

The contact device and the electromagnetic relay including it accordingto the exemplary embodiments of the present disclosure will now bedescribed with reference to drawings.

First Exemplary Embodiment

FIG. 1 is an external perspective view of electromagnetic relay 1according to a first exemplary embodiment of the present disclosure.FIGS. 2 to 4 are sectional views of electromagnetic relay 1. FIG. 2 istaken along line II-II, FIG. 3 is taken along line and FIG. 4 is takenalong line IV-IV. FIG. 5 shows a state where movable contactor 22included in FIG. 2 twists, and FIG. 6 shows, in an enlarged scale, astate where movable contactor 22 included in FIG. 4 twists. FIG. 7 showsa part of FIG. 6 in a further enlarged scale.

Electromagnetic relay 1 includes contact device 2, driving device 3, andbox-shaped housing 4. Housing 4 accommodates contact device 2 anddriving device 3.

Contact device 2 includes a pair of fixed terminals 21, movablecontactor 22, pressure-contact spring 23, spring receiver 24, movableshaft 25, adjusting portion 26, yoke 27, contactor holder 28, base(case) 51, connection body 52, and insulating member 53.

Each of fixed terminals 21 is made of a conductive material such ascopper and is formed into an approximate circular column. Each of fixedterminals 21 has fixed contact 211 at its bottom. Fixed terminals 21 areinserted into through-holes 511 of base 51, respectively, and are brazedto base 51 with their top end projecting from the upper surface of base51.

Fixed contacts 211 are fixed to the bottoms (lower ends) of fixedterminals 21, respectively. The fixed contacts 211 are aligned in afirst direction (Y direction) as shown in FIG. 3. These contacts 211 canbe formed integrally with fixed terminals 21, respectively.

Movable contactor 22 comes into or out of contact with the pair of fixedcontacts 211, and more specifically, in a second direction (Z direction)orthogonal to the first direction (Y direction). Movable contactor 22 isa flat plate extending in the first direction (Y direction), andincludes movable contacts 221 at the right and left ends of its uppersurface. In short, movable contacts 221 are formed at both ends in thelongitudinal direction of movable contactor 22. Each of movable contacts221 is located to oppose respective one of fixed contacts 211 with apredetermined spacing therebetween. Movable contactor 22 furtherincludes yoke 27, which is fitted into the approximate center of movablecontactor 22 in the first direction (Y direction).

Pressure-contact spring 23, which is a coil spring, is disposed betweenspring bearing 24 and yoke 27 so as to expand and contract in the seconddirection (Z direction). Yoke 27 has positioning projection 271, whichwill be described later. Positioning projection 271 is fitted into thetop end of pressure-contact spring 23 so that spring 23 can bepositioned with respect to yoke 27 and movable contactor 22.

Spring receiver 24 is made of, for example, an electrically insulatingmaterial such as resin and formed into an approximate rectangular plate.Spring receiver 24 has base part 241 whose upper surface has, at itsapproximate center, an approximately disk-shaped positioning projection242. Positioning projection 242 is fitted into the bottom end ofpressure-contact spring 23 so that spring receiver 24 is positioned withrespect to spring 23.

Movable shaft 25 moves contactor holder 28 in the second direction (Zdirection) so that movable contactor 22 comes into or out of contactwith the pair of fixed contacts 211. In other words, movable shaft 25moves along its axis so that movable contactor 22 comes into or out ofcontact with fixed contacts 211. More specifically, movable shaft 25 iscoupled to contactor holder 28 and moves in the second direction (Zdirection) so that movable contactor 22 comes into or out of contactwith fixed contacts 211. Movable shaft 25 has an approximately round barshape extending in the second direction. Movable shaft 25 is coupled tomoving core 34 of driving device 3 at a bottom end thereof, and tospring receiver 24 at a top end thereof. Shaft 25 is fixed to movingcore 34 while being inserted into through-hole 331 of fixed core 33,return spring 36, and through-hole 341 of moving core 34.

Adjusting portion 26 is made of a magnetic material and formed into, forexample, an approximate rectangular plate. Adjusting portion 26 ismounted at the approximate center of the upper surface of movablecontactor 22 in the first direction (Y direction) and is fixed tocontactor holder 28. Adjusting portion 26 may alternatively have a shapeother than a plate.

Yoke 27, which is made of a magnetic material, has an open top and anapproximately U-shaped cross section when seen from the first direction(Y direction). Yoke 27 is disposed under the approximate center ofmovable contactor 22 in such a manner as to sandwich this approximatecenter in the front-to-back direction (X direction). Yoke 27 haspositioning projection 271 formed into an approximate disk at theapproximate center of the bottom surface thereof.

Contactor holder 28 holds movable contactor 22 as shown in FIG. 6.Holder 28 has a pair of holding parts 281 each having bottom part 282and side part 283. Bottom part 282 and side part 283 are formed bybending a non-magnetic material. The pair of holding parts 281, whichare far apart from each other in the front-to-back direction, are formedintegrally with spring receiver 24. Spring receiver 24 is locatedbetween bottom parts 282 and pressure-contact spring 23. Thus, springreceiver 24 electrically isolates bottom parts 282 and pressure-contactspring 23.

The pair of bottom parts 282 and adjusting portion 26 sandwich movablecontactor 22, yoke 27, and pressure-contact spring 23 in the verticaldirection (Z direction). Consequently, pressure-contact spring 23 pushesmovable contactor 22 upward to bring its upper surface into contact withadjusting portion 26, thereby regulating the travel of movable contactor22 toward fixed contacts 211. Side part 283 extends upward from the edgeof bottom part 282. Side parts 283 oppose each other in the X direction.Side parts 283 are in sliding contact with movable contactor 22 and yoke27. Side parts 283 come into contact with adjusting portion 26 so as tosandwich adjusting portion 26 in the front-to-back direction. Bottompart 282 has, for example, a plate shape, but may alternatively haveother shapes. Side part 283 has, for example, a plate shape, but mayalternatively have other shapes.

As described above, adjusting portion 26 and yoke 27 are made of amagnetic material, while contactor holder 28 is made of a non-magneticmaterial. Consequently, when movable contacts 221 come into contact withfixed contacts 211, respectively, to supply a current to movablecontactor 22, a magnetic flux is generated around movable contactor 22and passes through adjusting portion 26 and yoke 27. As a result, amagnetic suction force acts between adjusting portion 26 and yoke 27.This force reduces the electromagnetic repulsive force generated betweenfixed contacts 211 and movable contacts 221, thereby reducing a decreasein the contact pressure between fixed contacts 211 and movable contacts221.

As shown in FIG. 3, base 51 is formed into a box with an open bottom andmade of a heat-resistant material such as ceramic. Base 51 accommodatesfixed contacts 211, movable contactor 22, and contactor holder 28. Base51 is provided with two through-holes 511 aligned in the right and leftdirection on an upper surface thereof.

Connection body 52 is brazed to the periphery of the opening of base 51at a first end thereof and to first yoke board 351 of yoke 35 in drivingdevice 3 at a second end thereof.

Insulating member 53 includes bottom part 531 and projection 532. Bottompart 531 is provided, at its approximate center, with insertion hole 533into which movable shaft 25 is inserted. Insulating member 53 is made ofan insulating material such as ceramic and synthetic resin and formedinto an approximate rectangular parallelepiped with an open top. The topend of the peripheral wall of insulating member 53 is in contact withthe inner surface of the peripheral wall of base 51. Consequently, atthe opening of base 51, insulating member 53 isolates the arc generatedbetween fixed contacts 211 and movable contacts 221 from the jointbetween base 51 and connection body 52.

In contact device 2, spring receiver 24 is disposed on the side ofmovable contactor 22 opposite to the side having the pair of fixedcontacts 211. Spring receiver 24 has base part 241, positioningprojection 242, projection 243, and partition wall 244. Partition wall244 is formed around movable shaft 25. More specifically, partition wall244 is, for example, cylindrical and extends from base part 241 towardinsulating member 53 along the axis of movable shaft 25.

Providing the above-described partition wall 244 suppresses foreignmatter generated while movable contactor 22 comes into or out of contactwith fixed contacts 211 from entering insertion hole 533.

As shown in FIG. 2, contact device 2 has a plurality of projections(four projections 512-515 in FIG. 2). Each of projections 512-515projects from base 51 at a respective position that opposes contactorholder 28 in a third direction (X direction) orthogonal to both thefirst direction (Y direction) and the second direction (Z direction).

As shown in FIG. 6, contactor holder 28 has upper area 28A and lowerarea 28B. Lower area 28B is more distant from movable contactor 22 thanupper area 28A in the second direction (Z direction). In contactorholder 28, lower area 28B is longer than upper area 28A in the thirddirection (X direction). More specifically, in contactor holder 28, thepair of holding parts 281 have a plurality of projected areas (fourprojected areas 284-287 in FIG. 6) in positions facing projections512-515, respectively.

Each of projections 512-515 has a curved end surface. On the other hand,contactor holder 28 has a flat surface facing projections 512-515. Thecurved surfaces and the flat surface come into stable contact with eachother.

The operation of contact device 2 will now be described with referenceto FIG. 3. First, when driving device 3 displaces (moves) movable shaft25 upward, spring receiver 24 and contactor holder 28 which areconnected to movable shaft 25 are also displaced upward. Together withthe displacement of spring receiver 24 and contactor holder 28, movablecontactor 22 moves upward. As a result, movable contactor 22 comes intocontact with the pair of fixed contacts 211 and provides electricalcontinuity between fixed contacts 211.

Driving device 3 will now be described in detail with reference to FIG.3. Driving device 3 is an electromagnet block and drives movable shaft25 so that movable contactor 22 comes into or out of contact with thepair of fixed contacts 211.

Driving device 3 includes excitation winding 31, coil bobbin 32, fixedcore 33, moving core 34, yoke 35, return spring 36, cylindrical member37, and bush 38. Driving device 3 further includes a pair of coilterminals (not shown) connected to both ends of excitation winding 31.

Coil bobbin 32 is made of a resin material and formed into anapproximate cylinder. Bobbin 32 includes flanges 321 and 322 at its topand bottom ends, respectively. Between flanges 321 and 322, there iscylindrical part 323 around which excitation winding 31 is wound. Theinner diameter of cylindrical part 323 is larger in the lower part thanin the upper part.

Both ends of excitation winding 31 are connected to a pair of terminalareas (not shown) formed on flange 321 of coil bobbin 32 and are alsoconnected to a pair of coil terminals via lead wires (not shown)connected to the terminal areas. The coil terminals are made of aconductive material such as copper and are connected to the lead wiresby soldering.

Fixed core 33 is made of a magnetic material and formed into anapproximate circular column and is fixed inside coil bobbin 32. Morespecifically, fixed core 33 is formed in cylindrical member 37accommodated in cylindrical part 323 of coil bobbin 32.

Moving core 34 is made of a magnetic material and formed into anapproximate cylinder. Moving core 34 is disposed in coil bobbin 32 so asto face fixed core 33 in the axial direction. More specifically, movingcore 34 is formed in cylindrical member 37, is fixed to movable shaft25, and moves in the vertical direction (Z direction) depending onwhether excitation winding 31 is energized or not. More specifically,moving core 34 moves upward when excitation winding 31 is energized, andmoves downward when the current to excitation winding 31 is interrupted.

Yoke 35 includes first yoke board 351, second yoke board 352, and a pairof third yoke boards 353. First yoke board 351 is disposed above coilbobbin 32, and second yoke board 352 is disposed below coil bobbin 32.Third yoke boards 353 extend from the right and left ends of second yokeboard 352 to first yoke board 351. First yoke board 351 is anapproximate rectangular plate and is provided with insertion hole 354 atthe approximate center of its upper surface. The top end of fixed core33 is inserted into insertion hole 354.

Return spring 36 is inserted both into the lower part of through-hole331 of fixed core 33 and the upper part of through-hole 341 of movingcore 34. Return spring 36 is disposed in a compressed state betweenfixed core 33 and moving core 34 so as to push moving core 34 downward.

Cylindrical member 37 has a bottomed cylindrical shape and accommodatedin cylindrical part 323 of coil bobbin 32. Cylindrical member 37 hasflange 371 at its top end. Flange 371 is located between flange 321 ofcoil bobbin 32 and first yoke board 351. Cylindrical member 37 hascylindrical part 372, which accommodates moving core 34 in a lower partthereof. Cylindrical part 372 further accommodates fixed core 33.

Bush 38 is made of a magnetic material and formed into a cylinder. Bush38 is fitted into a gap between the inner circumferential surface of thelower part of coil bobbin 32 and the outer circumferential surface ofcylindrical member 37. Bush 38 forms a magnetic circuit together withfirst yoke board 351, second yoke board 352, third yoke boards 353,fixed core 33, and moving core 34.

Housing 4 will now be described in detail with reference to FIGS. 1 and3.

Housing 4 is made of a resin material and formed into an approximaterectangular box. Housing 4 is composed of box-shaped housing body 41with an open top and box-shaped cover 42 covering the open top ofhousing body 41.

As shown in FIG. 1, housing body 41 has protrusions 411 on both lateralwalls Each of protrusions 411 is provided with an insertion hole usedfor screwing electromagnetic relay 1 to a mounting surface. As shown inFIG. 3, housing body 41 has step 412 along the periphery of the topopening Therefore, the inner dimensions of housing body 41 are larger inthe upper end than in the lower end.

Cover 42 has a box shape with an open bottom. Top surface 421 of cover42 is provided with partition board 422 which approximately divides topsurface 421 into right and left halves. Top surface 421 half-divided bypartition board 422 has a pair of insertion holes 423 into which fixedterminals 21 are inserted.

When contact device 2 and driving device 3 are accommodated in housing4, bottom cushion rubber 43 is inserted between second yoke board 352 ofyoke 35 and bottom part 413 of housing body 41. Between base 51 andcover 42, top cushion rubber 44 is inserted. Top cushion rubber 44 isprovided with insertion holes 441 into which fixed terminals 21 areinserted, respectively.

In electromagnetic relay 1 having the above-described structure, returnspring 36 slides moving core 34 downward, which in turn moves movableshaft 25 downward. Accordingly, movable contactor 22 is pushed down byadjusting portion 26, and moves downward together with adjusting portion26. Therefore, in the initial state, movable contacts 221 are away fromfixed contacts 211.

When excitation winding 31 is energized, and moving core 34 is slidupward by the suction of fixed core 33, movable shaft 25 connected tomoving core 34 also moves upward. As a result, spring receiver 24(contactor holder 28) connected to movable shaft 25 moves toward fixedcontacts 211, and in turn, movable contactor 22 also moves upward. Thismakes movable contacts 221 come into contact with fixed contacts 211,thereby providing electrical continuity between contacts 221 and 211.

When the current to excitation winding 31 is interrupted, return spring36 slides moving core 34 downward, and in turn, movable shaft 25 movesdownward. As a result, spring receiver 24 (contactor holder 28) movesdownward, and in turn, movable contactor 22 moves downward. This makesmovable contacts 221 apart from fixed contacts 211.

In contact device 2, the pair of movable contacts 221 are part ofmovable contactor 22 and formed integrally with movable contactor 22.However, as a modified example of the present exemplary embodiment, apair of movable contacts may be formed as a separate component frommovable contactor 22. Also in such a contact device, along with themovement of movable shaft 25, the movable contacts as a separatecomponent from movable contactor 22 move together with movable contactor22 and come into or out of contact with fixed contacts 211.

The twist of movable contactor 22 and contactor holder 28 around movableshaft 25 in contact device 2 will now be described with reference toFIGS. 5 to 7. The clockwise twist of movable contactor 22 and contactorholder 28 around movable shaft 25 results as follows. In this case,movable contactor 22 and contactor holder 28 do not come into contactwith the inner surface of base 51. Instead, projected area 284 comesinto contact with projection 512, and projected area 287 comes intocontact with projection 515. On the other hand, the counterclockwisetwist of movable contactor 22 and contactor holder 28 around movableshaft 25 results as follows. Movable contactor 22 and contactor holder28 do not come into contact with the inner surface of base 51. Instead,projected area 285 comes into contact with projection 513, and projectedarea 286 comes into contact with projection 514. Thus, when movablecontactor 22 and contactor holder 28 twist around movable shaft 25,contactor holder 28 comes into contact with projections 512-515.

As described above, even when the rotation (twist) of movable contactor22 is regulated, movable contactor 22 and base 51 have a sufficientspace therebetween in base 51, particularly in the upper area of base51. This provides an arc space for extending an arc generated betweenthe pair of fixed contacts 211 and movable contactor 22, therebyreducing arc-over. In particular, when base 51 has an open bottom, therotation of movable contactor 22 can be regulated at the base opening(bottom) formed with high accuracy, thereby having high accuracy of theregulation of the rotation.

As described earlier, it is preferable that at least the end surface ofeach of projections 512-515 is curved, and that contactor holder 28 hasa flat surface opposing projections 512-515. This configuration providesa stable contact between the curved and flat surfaces. As a result,movable contactor 22 can be prevented from being unreturnable to thestate before twist because of locking of a corner of movable contactor22 with respect to the inner wall of base 51 when the rotation ofmovable contactor 22 is regulated. In particular, base 51 made ofceramic is prevented from being chipped.

In contact device 2, contactor holder 28 is made in point contact withprojections 512-515 so that the rotation of holder 28 can be regulatedwith high accuracy.

In contact device 2, base 51 has projections 512 and 513 on a firstinner surface and projections 514 and 515 on a second. The first andsecond inner surfaces oppose each other in the third direction (Xdirection). Projections 512 and 513 are aligned in the first directionas well as projections 514 and 515 are. Alternatively, as shown in amodified example of the present exemplary embodiment of FIG. 8, base 51may have projections 512 and 513 on only one of the first and secondinner surfaces. In short, in the configuration of FIG. 8, base 51 hasprojections 512 and 513 aligned in the first direction (Y direction).Also in this configuration, movable contactor 22 and base 51 have asufficient space therebetween in base 51 regardless of whether movablecontactor 22 and contactor holder 28 twist either clockwise orcounterclockwise around movable shaft 25. This provides a sufficient arcspace and prevents arc-over regardless of the direction of twist ofmovable contactor 22.

Further alternatively, as shown in another modified example of thepresent exemplary embodiment of FIG. 9, base 51 may have a pair ofprojections 513 and 515 on it's the first and second inner surfaces,respectively. In short, base 51 may have each of projections 513 and 515on respective one of these opposite inner surfaces in a manner thatprojections 513 and 515 oppose each other in the third direction (Xdirection). Also in this configuration, movable contactor 22 and base 51have a sufficient space therebetween in base 51 regardless of whethermovable contactor 22 and contactor holder 28 twist either clockwise orcounterclockwise around movable shaft 25. This provides a sufficient arcspace and prevents arc-over regardless of the direction of twist ofmovable contactor 22.

When, for example, the twist of movable shaft 25 is previouslyrestricted to one direction, base 51 may have only one of projections512-515.

Second Exemplary Embodiment

FIG. 10 is an enlarged view of an essential part of an electromagneticrelay according to a second exemplary embodiment of the presentdisclosure. The contact device of the present exemplary embodiment isdifferent from contact device 2 of the first exemplary embodiment shownin FIG. 7 in the feature that the contact device includes resin members29 in contact with projections 512-515, respectively. FIG. 10 shows onlyone of resin members 29 in contact with projection 514. The samecomponents as in electromagnetic relay 1 of the first embodiment aredenoted by the same reference numerals, and hence the descriptionthereof will be omitted.

Contactor holder 28 of the present exemplary embodiment includes resinmembers 29. Resin members 29 are disposed so as to come into contactwith the respective projections 512-515 when movable contactor 22 andcontactor holder 28 twist around movable shaft 25. Resin members 29 areformed at the same time when the metallic portion of contactor holder 28is formed. The same functions as those of contactor holder 28 in thefirst exemplary embodiment are not described here.

In the above described configuration, resin members 29 are in contactwith projections 512-515, respectively, thereby reducing metal exposure,and hence, the probability of arc-over.

Resin members 29 may alternatively be formed separately from themetallic portion of contactor holder 28. In this case, resin members 29can, for example, be stuck to the metallic portion of contactor holder28.

What is claimed is:
 1. A contact device An electromagnetic relaycomprising: a pair of fixed contacts aligned in a first direction; amovable contactor configured to come that comes into or out of contactwith the pair of fixed contacts by a movement in a second directionorthogonal to the first direction; a contactor holder that holds themovable contactor; a movable shaft which that moves the contactor holderin the second direction so that the movable contactor comes into or outof contact with the pair of fixed contacts and twists about the movableshaft; and a base that case that comprises a plurality of wall portionsand a planar surface that covers upper edges of the wall portions on oneend of the case while leaving its other end open to form an open bottombox, wherein the case accommodates the pair of fixed contacts, themovable contactor, and the contactor holder, wherein the base havingcaseincludes a projection projecting from a position opposing the contactorholderfirst protrusion that projects from one of the wall portionstowards interior of the case in a third direction orthogonal to both thefirst direction and the second direction, and wherein the case and thefirst protrusion are integrally formed from same material; and a windingthat causes the movable shaft to move in the second direction dependingon whether the winding is energized or not, wherein the contactor holdercomes into contact with the projection first protrusion along the thirddirection when the movable contactor and the contactor holder twistaround the movable shaft.
 2. The contact device according to claim 1,wherein the contactor holder has an upper area and a lower area, thelower area is more distant from the movable contactor than the upperarea in the second direction, and the lower area has a larger lengththan the upper area in the third direction.
 3. The contact deviceaccording to claim 1, wherein the projection has a curved end surface,and the contactor holder has a flat surface opposing the projection. 4.The contact device according to claim 1, wherein the contactor holderhas a projected area at a position opposing the projection.
 5. Thecontact device according to claim 1, wherein the contactor holderincludes a resin member which comes into contact with the projectionwhen the movable contactor and the contactor holder twist.
 6. Thecontact device according to claim 1, wherein the projection is one of aplurality of projections aligned in the first direction, and the basehas the plurality of projections.
 7. The contact device according toclaim 1, wherein the projection is one of a pair of projections providedon a pair of inner surfaces of the base, opposing each other in thethird direction.
 8. An electromagnetic relay comprising: the contactdevice according to claim 1; and a driver which drives the movable shaftso that the movable contactor comes into or out of contact with the pairof fixed contacts.
 9. The contact device according to claim 1, theprojection comprising a plurality of projections, wherein, when themovable contactor and the contactor holder twist around the movableshaft in a first twist direction, at least one of the plurality ofprojections comes into contact with the contactor holder, and when themovable contactor and the contactor holder twist around the movableshaft in a second twist direction opposite to the first twist direction,a different at least one of the plurality of projections comes intocontact with the contactor holder.
 10. The electromagnetic relayaccording to claim 8, the projection of the contact device comprising aplurality of projections, wherein, when the movable contactor and thecontactor holder of the contact device twist around the movable shaft ofthe contact device in a first twist direction, at least one of theplurality of projections comes into contact with the contactor holder,and when the movable contactor and the contactor holder twist around themovable shaft in a second twist direction opposite to the first twistdirection, a different at least one of the plurality of projectionscomes into contact with the contactor holder.
 11. The electromagneticrelay according to claim 1, further comprising: a magnetic materialdisposed on a surface of the movable contactor, wherein the contactorholder further holds the magnetic material, the contactor holderincludes side parts that are disposed across from each other, themovable contactor is provided between the side parts, and each of theside parts includes: an upper portion facing the magnetic material, andtwo side portions extending downward from the upper portion.
 12. Theelectromagnetic relay according to claim 1, further comprising: amagnetic material disposed on a surface of the movable contactor; a yokedisposed in the case and under the movable contactor; and a springdisposed in the case and under the yoke, wherein the contact holderholds the magnetic material, the yoke and the spring.
 13. Theelectromagnetic relay according to claim 12, the case further includes asecond protrusion facing the first protrusion along the third direction,and the magnetic material is absent in an area between a peak of thefirst protrusion and a peak of the second protrusion.
 14. Theelectromagnetic relay according to claim 13, wherein the magneticmaterial is fixed to the contactor holder, and the movable contactor ispressed towards the magnetic material by the spring, and is held by thecontactor holder.
 15. The electromagnetic relay according to claim 12,wherein the magnetic material and the movable contactor are held by thecontactor holder and are a part of the contact holder.
 16. Theelectromagnetic relay according to claim 12, wherein: the case furtherincludes a third protrusion that is disposed adjacent to the firstprotrusion and projects towards interior of the case, and a fourthprotrusion disposed across from the third protrusion to face the thirdprotrusion, and the magnetic material is absent in an area between apeak of the third protrusion and a peak of the fourth protrusion. 17.The electromagnetic relay according to claim 1, further comprising: apair of fixed terminals, wherein each of the pair of fixed contacts isprovided to each of the pair of fixed terminals, and wherein the planarsurface includes a pair of through holes, each of the pair of throughholes accommodating each of the pair of fixed terminals.
 18. Anelectromagnetic relay, comprising: a pair of fixed contacts; a movablecontactor that comes into or out of contact with the pair of fixedcontacts; a magnetic material disposed on a surface of the movablecontactor; a contactor holder that holds the movable contactor and themagnetic material, wherein the contactor holder includes side parts thatare disposed to be across from each other, and wherein the movablecontactor is provided between the side parts; a movable shaft that movesthe contactor holder so that the movable contactor comes into or out ofcontact with the pair of fixed contacts and twists the contactor holder;a case that comprises a plurality of wall portions and a planar surfacethat covers upper edges of the wall portions on one end of the casewhile leaving its other end open to form an open bottom box,accommodates the pair of fixed contacts, the movable contactor, thecontactor holder, and the magnetic material, and includes a firstprotrusion that projects from one of the wall portions towards interiorof the case, wherein the case and the first protrusion are integrallyformed from same material; and a winding that is disposed outside of thecase and moves the movable shaft depending on whether the winding isenergized or not, wherein each of the side parts includes: an upperportion facing the magnetic material, and two side portions extendingdownward from the upper portion, and wherein the contactor holder comesinto contact with the first protrusion when the contactor holder twistaround the movable shaft.
 19. The electromagnetic relay according toclaim 18, wherein the case further includes a second protrusion disposedon a same surface that the first protrusion is disposed, wherein alength between a base point of the first projection that is closer to afirst corner of the case and a base point of the second protrusion thatis closer to a second corner of the case is longer than a length betweenthe two side portions, wherein the first protrusion projects towards theinterior of the case from the base point of the first projection, andwherein the second protrusion projects towards the interior of the casefrom the base point of the second projection.
 20. The electromagneticrelay according to claim 18, wherein the case further includes a thirdprotrusion that faces the first protrusion, and projects towards thefirst projection, and the pair of fixed contacts are absent in an areabetween a peak of the first protrusion and a peak of the thirdprotrusion.
 21. The electromagnetic relay according to claim 18, whereinthe magnetic material and the movable contactor are held by thecontactor holder and are a part of the contact holder.
 22. Theelectromagnetic relay according to claim 18, wherein each of the sideparts further includes a through hole surrounded by the upper portionand the two side portions, and not facing a peak of the first protrusionwhen the contact holder is not twisted.
 23. An electromagnetic relay,comprising: a case that comprises a plurality of wall portions and aplanar surface that covers upper edges of the wall portions on one endof the case while leaving its other end open to form an open bottom box,and includes a first protrusion and a second protrusion that is disposedacross from the first protrusion to face the first protrusion, whereinthe first protrusion projects from one of the wall portions towards thesecond protrusion and the second protrusion project from another of thewall portions towards the first protrusion, and wherein the case, thefirst protrusion and the second protrusion are integrally formed fromsame material; a pair of fixed contacts disposed in the case; a movablecontactor that is disposed in the case, and comes into or out of contactwith the pair of fixed contacts; a magnetic material disposed on themovable contactor and between the pair of the fixed contacts, whereinthe magnetic material is absent in an area between a peak of the firstprotrusion and a peak of the second protrusion; a yoke disposed in thecase and under the movable contactor; a spring disposed in the case andunder the yoke; and a contactor holder disposed in the case, and thatholds the pair of fixed contacts, the movable contactor, the magneticmaterial, the yoke and the spring, wherein the contactor holder comesinto and out of contact with the first protrusion or the secondprotrusion.
 24. The electromagnetic relay according to the claim 23,wherein the case further includes a third protrusion and a fourthprotrusion that is disposed across from the third protrusion to face thethird protrusion, wherein the third protrusion and the fourth protrusionproject towards each other, wherein the magnetic material is absent inan area between a peak of the third protrusion and a peak of the fourthprotrusion, and wherein a width of the magnetic material is smaller thana distance between the peak of the third protrusion and the peak of thefourth protrusion.
 25. The electromagnetic relay according to claim 23,wherein the magnetic material and the movable contactor are held by thecontactor holder and are a part of the contact holder.